Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific quantity comparison means
Reexamination Certificate
2008-03-18
2008-03-18
Jackson, Stephen W. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific quantity comparison means
C361S115000
Reexamination Certificate
active
11181718
ABSTRACT:
Provided is an apparatus and method for identifying a specific lost current transformer (CT) signal of number of CT signals provided by a corresponding number of CTs coupling a protective device to at least one protection zone. The method includes selectively providing pairs of first and second binary control signals corresponding to each of the CT signals in response to comparisons of RMS current changes of respective CT signals. A third binary control signal associated with a protection zone is provided in response to receipt of the pairs of first and second binary control signals. A first value for only one of the first binary control signals, a second value for all of the second binary control signals and the first value for the third binary control signal for a predetermined time indicates the loss of the CT signal corresponding to the first binary control signal having the first value.
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Cook Alex McFarron Manzo Cummings & Mehler, Ltd.
Jackson Stephen W.
Schweitzer Engineering Laboratories Inc.
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